This is a really complicated answer.

-In 2008, George Bush was really unpopular, but the party's conservative wing was still able to flex its muscles. John McCain had made his career being a center-right moderate. He disavowed the label later in his career, but he was considered a maverick for a reason. But by 2008, McCain had to veer right and embrace conservative ideology. His campaign stumbled badly, with the Palin pick, the mixed messaging, and the image of a candidate changing his political philosophy because he wanted to be president.

Obama capitalized on all that. Despite a very divded primary, the Obama and Clinton wings united. Obama was a fresh face and a blank slate who motivated black voters and young voters on an unprecedented level.

-Romney is somewhat of a similar story. You don't get to be governor of Massachusetts by being a conservative Republican. And again, you could see the party veering even further right, but nominating a moderate like Romney. But we're also deep into the Tea Party and the alt-right movement is beginning to fester.

-In another 2016, Trump is just an unpredictable wildcard. He holds no personal values other than coveting power and money, but he's willing to embrace negative campaigning in a way never before seen. At the same time, the Democrats nominate Hillary Clinton. The Republican Party had been preparing for her for 24 years, since Bill Clinton was elected in 1992. In contrast to her husband, Hillary Clinton isn't charismatic or as good at evading criticism. She has to combat decades of negative attacks against her, as well as a mountain of sexism and accusations of nepotism. And she ran a bad campaign. She made a couple of bad gaffes that made it easy for opponents to paint her as out of touch. You have to look at it from amoral, political lens. Calling voters stupid, or deplorable, isn't the way to earn votes. Should have stayed focused on the candidate.